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Invasive Science and Management 2012 5:436–442

Landscape-Scale Rehabilitation of Medusahead ( caput- medusae)-Dominated Sagebrush Steppe

Roger L. Sheley, Edward A. Vasquez, Anna-Marie Chamberlain, and Brenda S. Smith*

Producers facing infestations of invasive annual grasses regularly voice the need for practical revegetation strategies that can be applied across broad landscapes. Our objective was to determine the potential for scaling up the single- entry approach for revegetating medusahead-infested to broader, more heterogeneous landscape-scale revegetation of winter annual grass–infested rangeland. We hypothesized, when applied on a highly variable landscape scale, the combination of imazapic and seeding would provide highest abundance of perennial grasses and lowest amount of annual grasses. Treatments included a control, seeding of crested wheatgrass (‘Hycrest’) and Sandberg’s bluegrass, spraying (60 g ai ha21 imazapic), and a simultaneously applied combination of spraying and seeding. The HyCrest and Sandberg’s bluegrass seeding rates were 19 and 3.4 kg ha21, respectively. The treatments were applied to large plots (1.4 to 8 ha) and replicated five times, with each replication located in different watersheds throughout southeastern . This study shows that the single-entry approach can be scaled up to larger landscapes, but variation within establishment areas will likely be high. This procedure should reduce the costs over multientry treatment applications and make revegetating annual grass–infested rangeland across landscapes more affordable. Nomenclature: Imazapic; medusahead, Taeniatherum caput-medusae (L.) Nevski; crested wheatgrass, (L.) Gaertn. 3 Agropyron desertorum Gaertn. ‘Hycrest’; Sandberg’s bluegrass, secunda J.S. Presl. Key words: Invasive annual grasses, medusahead, cheatgrass, restoration, rangeland, one-pass system.

Winter annual grasses, such as medusahead [Tae- dominated by winter annual grasses is essential to niatherum caput-medusae (L.) Nevski], have invaded recovering the ecological goods and services once provided millions of hectares of rangeland throughout western by functioning healthy ecosystems (Sheley et al. 1996). ; they continue to spread at an alarming Effective management of medusahead-infested rangeland rate (Davies and Johnson 2008; Young 1992). These has been elusive because responses to management are invasive grasses displace desirable perennial grasses, reduce highly variable. Several studies have shown the effectiveness livestock forage, and accumulate large fuel loads that foster of imazapic for controlling medusahead (Monaco et al. frequent fires (Davies 2011; Davies and Svejcar 2008; 2005; Sheley et al. 2007). Monaco et al. (2005) found that Hironaka 1961; Miller 1996). Medusahead has major applying 140 g ai ha21(0.12 lb ai ac21) provided better negative effects on ecosystem function by reducing plant medusahead control than 70 g ai ha21(0.06 lb ai ac21) and and animal diversity, reducing suitable wildlife habitat, that a fall application was most efficacious. Similarly, 2 accelerating erosion, and altering nutrient cycles, hydro- Sheley et al. (2007) found rates from 35 g ai ha 1 2 2 2 logic cycles, and energy flow (Davies 2011; Davies and (0.03 lb ai ac 1) to 210 g ha 1(0.19 lb ai ac 1) can be Svejcar 2008; Olson 1999). Rehabilitation of rangeland effective in controlling medusahead, but variation in plant responses and longevity of the control is highly variable. DOI: 10.1614/IPSM-D-12-00030.1 For any long-term benefits, periodic and frequent * First and fourth authors: Rangeland Ecologist and Research applications must be applied, and costs probably prohibit Agronomist, U.S. Department of , Agricultural Research the sustainability of this approach (Sheley et al. 2011). On Service, Burns, OR, 97720; Second author: Research Rangeland medusahead-infested rangeland devoid of perennial grasses, Ecologist, Wildlife Consultants LLC, Ft. Collins, CO revegetation aimed at filling niches with desired species is a 82051; Third author: Assistant Professor, Oregon State University critical objective of ecologically based invasive plant Extension Malheur County, , OR 97914. Corresponding management (Sheley and Carpinelli 2005). Davies (2008) author’s E-mail: [email protected] demonstrated that perennial grasses were the critical

436 N Invasive Plant Science and Management 5, October–December 2012 managers need information about how a management Management Implications program based on small-scale localized plots is actually Managing invasive annual grass infestations on a large scale manifested across highly heterogeneous management units. remains a major impediment for successful rangeland restoration. Our objective was to determine the potential for using The high cost of treatments and low percentage of success often the single-entry approach on more heterogeneous land- keep managers from initiating management plans where large-scale scape-scale acreage for revegetating medusahead-infested infestations are present. In this experiment, we utilized a single- rangeland. We hypothesized that even when applied on a entry treatment of herbicide application and seeding on landscape- scale plots of medusahead- and cheatgrass-infested rangeland. highly variable landscape scale, the combination of We were interested in determining whether this method would imazapic and seeding would provide the highest abundance provide acceptable levels of control for the invasive grasses and of desired perennial grasses and the lowest amount of establishment of desired species. Our results suggest that the one- invasive annual grasses. pass system might be a suitable method for restoring invasive annual grass infestations and lower the cost of treatment by completing an herbicide application and seeding in a single entry Materials and Methods into the field. This study was conducted on five sites from 2008 through 2011 along the southeastern Oregon– border functional group to preventing medusahead re-establish- in Malheur County, OR (Jordan Valley). The specific ment. Revegetation can be successful on small plots in study area is located within the Owyhee High Plateau some cases, especially if a prescribed burn is applied before Major Land Resource Area (MLRA-25) and occurs within seeding and an herbicide application (Davies 2010). the Owyhee Ecological Province (Anderson et al. 1998) However, establishing desired species in annual grass– (42.9769uN, 2117.0347uW). Elevation ranges from about dominated areas has proven very difficult (Milton, 2004; 1,200 to 1,500 m across the five study sites. Rainfall occurs Rafferty and Young 2002), and revegetation of medusa- in the spring and sporadically in summer, and precipitation head-infested rangeland is often unsuccessful (Monaco et occurs mainly as snow in the winter. Precipitation was al. 2005; Sheley et al. 2007; Young 1992). The need for relatively higher compared with the mean during the spring practical revegetation strategies for annual grass–dominated of 2009 and 2011 (Figure 1a). During the 3 yr of the rangeland that can be applied across broad landscapes is study, the average air temperature for May through June at substantial, but more options are available than in the past. the Jordan Valley Soil Climate Analysis Network site We tested the potential for using the single-entry (Natural Resource Conservation Service National Water approach (simultaneous application of herbicide and seed and Climate Center) was relatively close to historic mean with one entry) developed for other invasive –infested temperatures (Figure 1b). Two sagebrush alliances typically systems (Sheley et al. 2012) for revegetating medusahead- are found within the study area: 1) Artemisia tridentata infested rangeland in an attempt to create a more practical Nutt. var. wyomingensis Beetle & Young,–Pseudoroegneria approach to revegetating rangeland (Sheley 2007; Sheley et spicata (Pursh) A. Love and 2) A. tridentata–Chrysothanmus al. 2001). In this early work to manage medusahead, viscidiflorus (Hook.) Nutt.–P. spicata. However, medusa- treatments included three seeding rates (none, and 13.2 head, cheatgrass ( L.), or both were the 21 21 (11.8) or 25.0 kg ha (22.3 lb ac ) of an even mixture of dominant herbaceous understory at each site, with P. all species), two herbicide applications (with and without spicata, elymoides (Raf.) Swezey, and Sandberg’s 21 21 52 g ai ha (0.05 lb ai ac ) imazapic), and two burning bluegrass ( J.S. Presl) as subdominate species. regimes (burned, not-burned) applied mid-October 2006 Soils were variable across the study area and included on two sites. This experiment was designed to minimize Aridisols and Mollisols and are generally well drained, variability and maximize our ability to detect statistical clayey or loamy, and shallow or moderately deep. differences. In that study, we found that simultaneous application of imazapic and seeding provided some Procedures and Experimental Design. We used a single- establishment of desired species where they were absent. entry (one-pass) restoration strategy to enhance the success However, little is known about the effectiveness of this of establishing desired species and reduce the costs system applied across landscape-scale management units. associated with multi-entry strategies (Sheley et al. 2001). Conservation management practices are highly variable Treatments included (1) single-entry herbicide and because of spatial heterogeneity that occurs across compli- seeding, (2) herbicide only, (3) seeding only, and (4) no- cated rangeland landscapes (Bestelmeyer et al. 2012). herbicide/nonseeded control. This large-scale study was Scaling up management programs on the basis of small- arranged in a randomized block design and replicated plot experimentation may be misleading because the across five different sites throughout the Jordan Valley area; research does not account for natural variation across the treatments were not replicated at the sites. Sites were landscapes (Kreuter et al. 2005). To make wise decisions, replicates for this experiment. Plot sizes varied at each site

Sheley et al.: Landscape-scale rehabilitation of medusahead N 437 but were a minimum of 1.4 ha to nearly 8 ha. The seed mixture included: 1) crested wheatgrass [Agropyron crista- tum (L.) Gaertn. 3 Agropyron desertorum Gaertn. ‘Hy- crest’], which is an improved cultivar of crested wheatgrass that was developed from a hybrid between A. cristatum and A. desertorum, and 2) Sandberg’s bluegrass. The crested wheatgrass and Sandberg’s bluegrass seeding rates were 19 and 3.4 kg ha21 (16.9 and 3.03 lb ac21), respectively. Treatments were implemented mid-November 2008 (fall dormant) using a no-till rangeland drill. Grasses were seeded to a depth of 4 mm and packed with a pipe pulled directly over each drill row. Seedling establishment was unsuccessful in 2008. Early winter season drought in 2008 to 2009 is thought to have been the primary reason for poor establishment; consequently, these treatments were repeated in mid-November of 2009 at each of the five sites. Additionally, seeding rate for crested wheatgrass was increased to 24.6 kg ha21 (21.9 lb ac21) in 2009. In plots designated to receive herbicide, imazapic (Panoramic 2SL, Alligare LLC, 13 N 8th Street, Opelika, AL) was applied at a rate of 60 g ai ha21 (0.05 lb ai ac21). The herbicide application occurred in the same entry as seeding using a front-mounted spray applicator calibrated to deliver a total volume of 234 L ha21 (25 gal ac21). Sampling occurred in mid-July 2010 and 2011. Density was sampled by counting the number of annual grass and perennial grass tillers in 20 randomly located 0.25-m22 (2.7 ft22) frames in each plot. In addition to counting density in 2010 and 2011, each frame was clipped to ground level to estimate biomass. were separated by species, dried (60uC [140uF] for 48 h), and weighed. Data Analysis. A generalized, linear, mixed model was implemented using SAS Proc Glimmix with either the Poisson or Negative Binomial distribution used to model the responses (SAS 2009). Year, treatment, and the inter- action were considered fixed effects, and rep and rep by treatment were the random effects. When the year by treatment effect was not significant, Tukey’s adjustment was used for making comparisons among the treatment main effect means. When the year by treatment effect was significant, comparisons among treatments within years were made using the Bonferroni adjustment for multiplicity.

Figure 1. (a) Total precipitation for each season during the study Results period collected from a centralized weather station in Jordan Valley. (b) Average air temperatures for each season during the Perennial Grasses. Crested Wheatgrass. ANOVA indicated study period collected from a centralized weather station in no treatment affected crested wheatgrass density using Jordan Valley. The dashed lines represent the mean values for multiple comparisons, but the individual treatment each season over the previous 18 yr that data were collected. comparison indicated that those plots sprayed and seeded had higher density than the control (P , 0.001). The sprayed and seeded plots had 41 plants m22, with only 0.38 plants m22 where no treatment was applied. However, crested wheatgrass biomass was higher than all

438 N Invasive Plant Science and Management 5, October–December 2012 Figure 2. Effects of treatments on crested wheatgrass biomass in 2010 and 2011 combined. other treatments where spray and seed was applied simultaneously (Figure 2).

Sandberg’s Bluegrass. Across years, tiller density of Sand- berg’s bluegrass was higher after the spray and seed combination was applied than in the control and where seeded with the herbicide, but it was not higher than spraying alone (P 5 0.005; Figure 3a). Sandberg’s bluegrass biomass was affected by treatments, but the effect depended on the year of sampling (P 5 0.031). In 2010, there was no response to any treatment, but spraying and spraying plus seeding more than doubled Sandberg’s bluegrass biomass in 2011 (Figure 3b).

Associated Grasses. No treatment or treatment combinations produced any detectable effects on the associated perennial grass, primarily P. spicata and E. elymoides density (P 5 0.25) or biomass (P 5 0.36).

Annual Grasses. Medusahead. The effects of treatments on medusahead density (P 5 0.002) and biomass (P , 0.001) depended on year, and these parameters followed a similar pattern (Figure 4a). In 2010, medusahead was reduced to nearly zero after the spray or spray plus seeding treatments. By 2011, only the spray plus seeding combination continued to control medusahead, which was lower than all other treatments at that time (Figure 4b).

Forbs. No treatment or treatment combination affected Figure 3. Effects of (a) treatments on Sandberg’s bluegrass tillers perennial , a mix of many species, but primarily in 2010 and 2011 combined and (b) the interaction of years on Achillea millefolium L., Phlox sp., and Crepis sp. (P . Sandberg’s bluegrass biomass by treatment. 0.35). However, seeding had a temporary effect on annual density (P 5 0.056) and biomass (P 5 0.016; Figures 5a and 5b). Annual forbs were also a mix of many different species but were primarily nonnative, such as Sisymbrium sp. and Lactuca sp. Annual forb density and biomass nearly tripled over other treatments where plots

Sheley et al.: Landscape-scale rehabilitation of medusahead N 439 Figure 4. Effects of treatments in each year on medusahead (a) tillers and (b) biomass. were seeded in 2010, and annual forb biomass was higher Figure 5. Effects of treatments in each year on forb (a) number in plots that were seeded and sprayed than in the control. of plants and (b) biomass.

increasingly clear that revegetation is central to recovering Discussion the effects associated with medusahead invasion, especially Providing viable and cost-effective options for managing in areas devoid of desired grasses (Davies and Svejcar 2008; medusahead has been identified as a critical need by Sheley et al. 2007). The aim of revegetation is to create ranchers in southeastern Oregon (Johnson et al. 2011). It is invasion resistance within the plant community by

440 N Invasive Plant Science and Management 5, October–December 2012 maximizing niche occupancy and biomass production amount of annual grasses. The two seeded species used in (Borman et al. 1991; Davies 2008; James et al. 2008). this large-scale study had the highest density and biomass Thoughtful but complex integrated annual grass manage- in areas that received a simultaneous combination of ment strategies combining , fire, and seeding imazapic and seeding, and prolonged medusahead control have been shown to create a diverse plant community that was highest after this treatment combination. It should be resists future invasions (Johnson and Davies 2012; Sheley clearly noted that spring conditions during this study were et al. 2007). However, complex revegetation is costly, and wetter than average, and these results might not reflect the likelihood of failure is so high that managers are often those for dryer years. directed to aim efforts toward situations with potentially The current focus of landscape-scale management often greater success, such as prevention or applying herbicides in assumes the landscape is relatively homogeneous, which is areas where some residual desired species would be released clearly not the case on complex rangeland (Brown et al. from after medusahead control (Davies and 2002; -Allen et al. 2006). In addition to our Johnson 2008; Davies and Sheley 2011). After more than a hypotheses, it was also reasonable to expect that the century of invasion, large monocultures of medusahead standard errors of the mean responses would be large, dominate millions of hectares across the western United reflecting the variation caused by heterogeneous landscapes. States and will likely continue to increase until a practical In our small-plot study, standard errors ranged from 20% and successful revegetation strategy is developed. to 10% of the mean (Sheley et al. 2012). In this study, Some of the expense and difficulty associated with standard errors ranged from 50% to the size of the mean revegetation of medusahead-infested rangeland arises when across all responses. Spatial heterogeneity likely elicits complex strategies require multiple entries into the variable responses across landscapes and increases the management unit and repeated attempts at revegetation variance, similar to that across sites (Fulendorf and Smeins after failure (Sheley et al. 2012). In traditional revegetation 1998; Turner and Chapin 2005). In spite of high variances, processes where medusahead infestations occur, the area is the simultaneously applied combination of imazapic and burned in the fall to remove litter and create access to the seeding provided the greatest abundance of perennial soil surface, then sprayed with imazapic, and seeded before grasses and the lowest amount of annual grasses. However, the onset of severely cold temperatures. Each application is managers should expect that large-scale application of this usually conducted independently. To lower the expense single-entry revegetation approach will create a diversity of associated with this multi-entry approach, Sheley et al. densities of desired species across heterogeneous landscapes. (2001) and Sheley (2007) found that the combination of Revegetating medusahead plant–dominated rangeland is spraying an herbicide and seeding in a late-fall, dormant, central to managing invasive species. The current multi- single-entry application successfully established several entry approach is too expensive because of the high cost of wheatgrass species in knapweed infestations. Sheley et al. application and low probability of success. Common (2012) tested the single-entry approach for revegetating multientry approaches often include a fall herbicide medusahead-infested rangeland using small plots. In that application, followed by burning or disking the following study, we found that the simultaneous application of spring and a separate seeding operation in the spring or fall imazapic and seeding provided establishment of desired after disking. In small plots, Sheley et al. (2012) developed species where they were absent. However, the evidence was a single-entry program that simultaneously applied im- only partially supportive because establishment depended azapic with a fall-dormant seeding to enhance the on the site and its environmental conditions. In that study, establishment of desired species in areas dominated by data supported other investigations, suggesting imazapic annual grasses. However, the results of that study raised combined with seeding can be an effective strategy for concern over the procedure’s effectiveness across heteroge- revegetating medusahead-infested rangeland, but reempha- neous landscapes. This study shows that the single-entry sizes the difficulty in predicting the conditions under which approach can be scaled up to larger landscapes, but desired vegetation can be successfully established (Davies variation within the establishment area will likely be high. 2010; Sheley et al. 2005). We were encouraged by enduring medusahead control and Variation in establishment of desired species using the perennial grasses biomass increases evident after two single-entry approach occurs widely among sites (Sheley et seasons posttreatment. This trend indicates longer term al. 2012). Variation across landscape is a ubiquitous feature control of medusahead. As with all rangeland management, of rangeland that must be considered in large-scale it is critical that producers practice adaptive management rangeland management (Bestelmyer et al. 2011). In this and continue to monitor sites after applying treatments. study, we found evidence to support the hypothesis even Ultimately, this procedure should reduce the costs of when applied on a highly variable landscape scale, the multientry treatment applications and make revegetating combination of imazapic and seeding would provide the annual grass–infested rangeland across landscapes more highest abundance of perennial grasses and the lowest affordable. The obvious implication is that any time a less

Sheley et al.: Landscape-scale rehabilitation of medusahead N 441 expensive, more effective alternative is available, producers Johnson, D. D., K. W. Davies, P. T. Schreder, and A. M. Chamberlain. are more likely to initiate management of medusahead 2011. Perceptions of ranchers about medusahead (Taeniatherum caput-medusae (L.) Nevski) management on sagebruch steppe before infestations take over healthy rangeland. . Environ. Manage. 48:400–417. Krueter, U. P., H. E. Amestoy, M. M. Kothmann, D. N. Ueckert, W. A. Mcginty, and S. R. Cummings. 2005. The use of brush Acknowledgments management methods: a Texas landowner survey. J. Range Manage. The authors offer their sincere thanks to the cooperating 58:284–291. landowners in Jordan Valley in Oregon and Idaho, including Miller, H. C. 1996. Demography of Medusahead on Two Soil Types: Mike Baltzor, Clint Fillmore, Robert Fretwell, Mark Mac- Potential for Invasion into Intact Native Communities. M.S. thesis. 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